Archery bows have long been used by hunters and sportsmen. A conventional archery bow is formed from a single piece or pair of elongated arms that extend from a central handle. A bow string extends between the ends of the elongated arms and placed in a highly-tensioned position. Opposite ends of a loaded arrow are supported by the handle and bow string. Drawing the bow string increases the potential energy within the bow, placing an arrow in a launch-ready state.
In some archery bow designs, the arms are fixed and bend when the bow string is pulled. In this type of bow, often called a recurve bow, pulling the bow string to bend the arms raises the potential energy within the bow. The increased potential energy is stored primarily in the flexed arms until the bow string is released. Accordingly, the force required to draw the bow string and the resulting arrow-launch force are products of the arm materials and geometry. Unfortunately, many archers are not able to use high-powered versions of this type of bow. For example, versions that gain power from long, relatively-pliant arms may be too cumbersome for use by many individuals. Alternately, high-powered versions that use compact, relatively-stiff arms may require more pull force than many archers can provide. Recurve bow have the additional drawback of limited adjustability. Once the bow is made, it is often difficult, if not impossible, to vary the bow's operating characteristics.
One example of a recurve bow is disclosed in U.S. Pat. No. 3,674,001. This archery bow has both primary arms and auxiliary arms. The arms are flexible, and the auxiliary arms are positioned to resist motion of the primary arms. This cooperative arrangement produces a relatively higher-powered bow, when compared with bows including the primary arms only.
In other bow designs, such as U.S. Pat. No. 3,989,026, the arms are rigid and the bow string is connected to a system of cables, springs, and pulleys. In this type of bow, pulling the bow string increases the potential energy within the bow by loading the springs. The increased energy is stored primarily within the springs until the bow string is released to launch an arrow. This type of bow, often called a compound bow, is usually adjustable. Altering the springs, for example, will change the required bow string pull weight and resultant arrow-launching forces. Additionally, the pulleys may have non-circular perimeters that provide a mechanical advantage that lowers the force required to keep the bow string pulled back in a ready-to-launch position. A compound bow that relies on a network of cables and pulleys, many compound bows can not be readily dismantled. Although some compound bows have detachable arms, the included cables can make removing and reattaching the arms difficult or maintenance-intensive. Additionally, although compound bow characteristics are more a function of spring forces than arm length, there is a minimum bow length which be maintained to create a useful device. As bow length decreases, so to does the angle between the arrow and bow string. If this angle is too small, the bow string will pinch the archer's fingers when the bow string is pulled back during use.
As mentioned above, U.S. Pat. No. 3,989,026 is an example of a compound archery bow. In the '026 device, a bow string is directed around the bow frame by a series of guides; the bow string is attached to a single tension-producing member. The single tension producing member ensures uniform tension throughout the bow. By including only one such member, this bow eliminates tension variances that are common in bows with two or more tension-producing members. The bow arm angles may be adjusted with respect to a central beam, and the arms may also be removed.
U.S. Pat. No. 4,903,677 discloses yet another compound bow. The bow has a rigid frame and energy is stored within flat, coiled springs mounted on the frame. Applying a tensile force to the bow string increases energy within the flat coiled springs. The energy is, in turn, transferred to a bow string to launch an arrow.
Another type of bow, such as that depicted in U.S. Pat. No. 3,744,473, includes design elements borrowed from both recurve and compound bows. This type of hybrid bow typically has rigid, pivoting portions attached to a fixed handle. These hybrid bow designs employ the cable systems found on compound bows and incorporate a modified version of the moving limb motion common to recurve bows. As a result, hybrid bows are adjustable to a degree, and do not rely solely on limb flexibility for power generation. However, such hybrid bows are difficult to store and dismantle.
The '473 patent discloses a hybrid archery bow having rotatable, spring-loaded arms. The arms are connected to a central beam by rotating wheels. Cables extend between the wheels to ensure that the arms rotate in uniform, yet opposite, directions when the bow string is pulled.
What is needed in this art is an archery bow that encompasses the features of the known bow designs, while overcoming the difficulties faced so far. The bow should be simple in construction, so that it may dismantled for easy storage and travel. Additionally, the bow should be lightweight and adjustable so that it may be used in a variety of situations by archers of varying strength and skill. Finally the bow should be capable of high-powered configurations without producing cumbersome dimensions or necessitating unreasonable pull weights.